In solids/liquids separation equipment a driven screw (Archimedes) is commonly used for the conveyance and compression of materials requiring high pressure for the separation of the liquids from the solids material. One such application would be an oil screw press which generates a mostly radial compression force by reducing the flight spacing and/or the bore diameter in conjunction with the screw diameter.
When a single flight screw is utilized in a high pressure pump application, a radial load occurs due to the high percentage of the tangential load that is focused along a single plane perpendicular to the axis of the screw center. As the axial load increases, the tangential load imbalance increases producing a greater radial load that increases exponentially.
Typical methods of neutralizing the radial loads are double flight methods. The first being double flights along the entire length of the screw ending 180° apart in the same perpendicular plane, one other being a second flight commencing from the same perpendicular plane as the primary discharge end at 180° to the primary flight and wraps helically back along only a portion of the screw.
These two methods successfully neutralize damaging radial loads. Both methods have negative aspects that make them impractical for Washer Compactor application. The first method requires the two flights to be wrapped helically at a very steep incline plane in order to achieve the flight spacing needed. The angle at which the flight end pushes the debris into the high pressure zone is inefficient causing the power requirements to increase beyond acceptable limits.
The second method utilizes an acceptable incline plane on the primary flight to achieve the proper flight spacing, however, the second flight portion used to balance the loads at the end of the screw effectively cuts the flight spacing in half creating a jam point for large debris that has been allowed to enter the screw. The only way around this is to preprocess the debris though a grinder before it enters the screw, thus controlling the debris size. In applications where the expense and need for a grinder is unwarranted, a single flight screw is the preferred method.
With regard to U.S. Pat. No. 7,958,820, that issued to Terry Duperon on Jun. 14, 2011, the novel screw end design utilized is engineered to balance the tangential loads with balanced axial loading along a single flight, eliminating the corresponding radial load. By eliminating the radial load, the power input requirements are reduced by as much as 40% in this particular application of the technology.
In order to balance the tangential loads, the screw end is designed to produce 50% of the tangential force at the screw flight end. The remaining 50% is produced 180° radially from the screw flight end in a position that is one half of a lead frost the end along the same incline plane. This patent is hereby incorporated by reference for what it teaches about the manufacture and use of compactors.
Other prior art devices can be found in U.S. Pat. No. 3,062,129, that issued to Wandel on Nov. 6, 1962; U.S. Pat. No. 3,760,717, that issued to Demilt, et al on Sep. 25, 1973; U.S. Pat. No. 4,520,724, that issued to Costarelli on Jun. 4, 1985; U.S. Pat. No. 4,779,528, that issued to Bruke on Oct. 25, 1988; U.S. Pat. No. 5,337,658, that issued to Bruke on Aug. 16, 1934; U.S. Pat. No. 5,611,268, that issued to Hamilton on Mar. 18, 1997, and U.S. Pat. No. 6,550,376, that issued to Johnston on Apr. 22, 2003.